Elton John last night shocked fans after revealing he can no longer see out of either eye.
Attending a gala performance of his musical The Devil Wears Prada in London, the 77-year-old admitted he was physically unable to watch the show.
It came just weeks after the musician admitted a severe eye infection he contracted in July in France left him blind in his right eye, with 'limited vision' in his left.
'Now, I have lost my sight and I haven't been able to see the performance but I have enjoyed listening to it,' Elton, famous for his show-stopping glasses, said.
Eye infections may seem like a relatively minor – but inconvenient – health issue. Conjunctivitis is among the most common.
Yet others can develop into something far more serious, with sufferers experiencing symptoms from itching and swelling to vision loss.
In rare cases, infections can even lead to blindness.
Here MailOnline reveals how to spot the earliest warning signs of a common infection that could cost you your sight.
Conjunctivitis produces sticky pus or makes eyes feel gritty and is extremely contagious.
It happens when blood vessels in the conjunctiva — the thin outermost membrane surrounding your eyeball — become infected by bacteria or a virus and dilates.
Most viral conjunctivitis settles in two to three days, but some can last for two to three weeks.
The NHS-recommended treatment is simply a hot compress — soaking cotton pads in cooled, boiled water and gently wiping eyelashes to clean off crusts.
In severe cases, however, the infection can threaten sight permanently.
Hyperacute bacterial conjunctivitis is a rapidly developing type of conjunctivitis typically caused by infection with Neisseria gonorrhoeae — a a sexually transmitted disease.
Symptoms, which can develop within 12 hours of infection, often include a burning or gritty sensation in the eye and large amounts of pus repeatedly leaking from the eye.
Dr Francis Mah, an ophthalmologist in La Jolla, California, said: Hyperacute bacterial conjunctivitis is accompanied by a copious amount of green or gray mucus.
'If you take a tissue and wipe some of it away, it is back immediately. It is typically unilateral, although it can be bilateral.
'There can also be significant eyelid swelling and redness of the eye.'
Treatment for this type of conjunctivitis, involving drops and oral medication, might last for several weeks.
Without treatment, however, corneal infiltrates are one possible complication.
This is a type of inflammatory response in your cornea that can cause pain, cloudy vision, and light sensitivity.
Severe inflammation can lead to corneal melting — when layers of cornea dissolve putting patients at risk of ulcers.
According to the NHS, left untreated, a corneal ulcer — open sores in the outer layer of the cornea — can permanently damage vision and cause blindness if the infection spreads inside the eye.
Uveitis, another rarer eye infection, can also prove serious causing vision loss or blindness if left untreated.
The condition, which affects up to five in every 10,000 Brits each year, is inflammation of the uvea — the central layer of the eyeball that transports blood to the retina and transmits images to the brain.
Common symptoms include small dark spots or squiggly lines that float across your vision, eye pain, red eyes or sensitivity to light.
Some people may not notice any symptoms and so uveitis can be undetected for several weeks or months.
However, without treatment it can trigger raised eye pressure, retinal detachment or macular edema — a condition that occurs when fluid and protein build up in the macula (in the centre of the retina that's responsible for fine details) causing it to swell and thicken.
Contact lens wearers are also at greater risk of one other eye infection, acanthamoeba keratitis.
The preventable infection causes the front surface of the eye, the cornea, to become painful and inflamed and contact lens wearers are most at risk.
Early symptoms are similar to other eye infections including redness, light sensitivity and excessive watering.
But left untreated, the pathogen can burrow into the cornea, scarring its surface and causing blindness over a period of months.
It can get into the eye while bathing or showering, and if contacts are being worn during these activities, the chances of infection increases dramatically.
Even leaving contacts in overnight can increase the risk.
This is because small numbers of acanthamoeba, which causes the infection, can be transferred into the eyes if a person washes their hands then touches their face.
If acanthamoeba keratitis is caught early, doctors can treat it easily with eyedrops. It cannot be treated with antibiotics.
Experts advise anyone experiencing any early symptoms to stop wearing contact lenses and get in touch with their GP or optometrist right away.
In September, Elton John revealed he had been 'dealing with a severe eye infection' that had left him with 'limited vision in one eye'.
But speaking at a gala performance of The Devil Wears Prada: The Musical last night, he said he was unable to watch the show he wrote the music for, having lost his eyesight.
The West End production hosted a charity gala for the Elton John AIDS Foundation.
The musician, accompanied by his husband, said: 'As some of you may know I have had issues and now I have lost my sight.
'I haven't been able to see the performance but I have enjoyed it.'
He added: 'To my husband who's been my rock because I haven't been able to come to many of the previews... it's hard for me to see it but I love to hear it and it sounded good tonight. Thank you for coming.'
In an interview with ABC News last week he also admitted that issues with his sight had put his new album on hold.
Asked last week when his new album with Bernie Taupin, which he announced last year, would come out, Sir Elton said: 'It's been four months now since I haven't been able to see, and my left eye is not the greatest.
'So there's hope and encouragement that it will be OK, but it's... I'm kind-of stuck at the moment, because I can do something like this [an interview], but going into the studio and recording, I don't know, because I can't see a lyric for a start.
'We're taking initiative to try and get it better but at the moment that's really what we're concentrating on.
'It's never fortunate for anything like this to happen, and it kind of floored me. And I can't see anything, I can't read anything, can't watch anything.'
As well as his current sight issues, Elton has faced a multitude of other health hurdles, after he had both knees replaced as well his right hip following a fall, which forced him to delay his farewell tour in 2021.
Sir Elton, who was diagnosed with type 2 diabetes in the early 2000s, also recently embarked on a healthy-eating lifestyle change.
